Conventionally, an ultrasonic Doppler blood flow measuring device (color flow device), which enables measurement of blood flow distribution and blood flow velocity within a biological body by using the Doppler phenomenon of ultrasonic waves and displays the blood flow velocity, in correspondence to a predetermined color, by superimposing a black and white, two-dimensional cross-sectional image therewith, is known.
FIG. 5 is a block diagram of an example of a configuration of an ultrasonic Doppler blood flow measuring device according to prior art. The ultrasonic Doppler blood flow measuring device has a probe 2 for performing transmission and reception of ultrasonic waves to a biological body. An ultrasonic pulse is irradiated from a transmitting unit 1 to the blood flowing within the biological body, and the probe 2 again receives an echo of the ultrasonic pulse reflected by the blood. The echo of the ultrasonic pulse is converted into an electrical signal by the probe 2 and supplied to a receiving unit 3. After digitalization or beamforming by the receiving unit 3, the signal is phase-detected by a phase detecting unit 4 and becomes a Doppler-shift signal comprising information on the Doppler-shift due to blood flow.
The Doppler-shift signal is supplied from the phase detecting unit 4 to a wall filter 5. In wall filter 5, signals from unnecessary tissues which are low-frequency signal components are removed, and furthermore, in a velocity calculating unit 6, blood flow information, such as blood flow velocity data, blood echo intensity data, blood flow velocity variance data, and the like, is determined based on the signal subsequent to processing by the wall filter 5. This blood flow information is smoothing-processed by a filter 7, supplied to a digital scan Converter (DSC) 8, and coordinate-converted into a shape adhering to ultrasonic scanning.
In addition, a B-mode image (ultrasonic cross-sectional image) signal (B-mode signal) is supplied from an envelope detecting unit 9 to DSC 8, in the same way, and the DSC 8 not only coordinate-converts the supplied image data into a shape adhering to ultrasonic scanning, but also combines B-mode signal and blood flow information and shows a two-dimensional blood flow image on a monitor 10.
The blood flow velocity data comprised in the blood flow information is data which has a possibility of generating an aliasing phenomenon based on the Nyquist theorem. With regards to this measurement of blood flow velocity data having this aliasing, a method, for example, for performing filter processing with an arbitrary order after determining aliasing and performing corrections is disclosed in the following Patent Document 1 as a method for filter processing in filter 7.
Patent Document 1: Japanese Patent Application Publication No. 4-161146 (Heisei)